Thread gauging



Nv..3,1931. HARNESS i www? l THREAD GAUGING' Filed May 18, 1927 lO Sheets-Sheet l @WMM/M7 ,A

Nov. 3, 1931. .1 HAR-mass THREAD GAUGING Fill-2d May 18 1927,7

l0 Sheets-Sheet 2 dame? 7? Jai/wee@ Jemr @W @W7 News, v1931. l HARNESS 1,829,797

THREAD GAUGING I Filed May 18, 1927 lO SheehS-Sheet` 3 NOV. 3, 1931. 1.A HARTNESS 1,829,797

THREAD GAUGING Filed lMay 18, 1927 10 Sheets-Sheet 4 .56. I 246 Je@ @4 b v Mw@ www JZ@ Nov. 3, 1931. y J HARTNESS 1,829,797

THREAD GAUGING Filedy May 18, 1927 10 Sheets-Sheet 5 Za/67%?? Jw M73 www J. HARTNESS THREAD GAGING Nov. 3, 1931.

'l0 Sheets-Sheet 6 I fJmwL/ Filed May 18, 1927 Nov. 3, 1931 J. HARTNEss 1,829,797

THREAD GAUGI NG Filed May 18. 1927 lO Sheets-Sheet 8 Inl/6752571' j] lbw I v WWJJ :Q1/w( LM f7 44% Nov. 3, "1931. .1. HARTNESS THREAD GAUGING Filed May 13, 1927 10 Sheets-Sheet 9 v 7,9306 @www dfazeew Nov. 3, 1931. J. HARTNESS THREAD GAUGING 10 Sheets-Sheet lO Filed May 18, 1927 Patented Nov. 3, 1931 JAMES HARTNESS, OF SPRINGFIELD, VERMONT THREAD GAUGING Appncatin med May 1s,

One or' the most important phases of standardization of screw thread products is that of interchangeability, so that the products made in different parts of a manufacturing plant e' or in dierent manufacturing plants at a may be varied beyond predetermined limits,

for a certain class of fit. Important among these elements are major diameter, pitch diameter, minor diameter, angle of thread, and. pitch or l'ead. A variation in any one of these elements of a screw thread from a fixed standard for any size will prevent a perfect lit.v j v Heretofore the suitability of threaded parts for interchangeability Within a given class .of fit has been tested by the use of various forms of gauges termed Go and Not go. If the threaded member lwill be acceptable by the,Go gauge and unacceptable by the Not go gauge it has beenv passed asv suiciently accurate. This condition, however, does not necessarily signify that each of the Various elements, for which there are tolerance limits is actually within such limits, since Varia tion in one may, to a greater or less extent1 offset variation in another.. For example, an excessively long or shortlead in a screw will' give an effect of increased pitch diameter in the closeness of engagement of theescrew in a standard nut and in some types of Go gauge.

Another deficiency of the Go and Not lgo gauges is the fact that if the threaded work is` accepted by the Go gauge and refused by the Not go gauge there is nothing to indicate how near the work is tol being refused by the Go gauge and accepted by the Not go gauge; that is, how near its-dimensions are to the standard. It is desirable, however, to determine a position between the upper and lower tolerance limits which permits the widest departures therefrom without causing rejection of the Work and which, when the thread forming machine is oncead- 1927. serial N0. 192,236.

justed to it, Will permit the machine to run longest without overrunning the boundaries of tolerance.

According to the present invention, therefore, gauging means are rovided by which the nearness to this desira le position Within the tolerance range of certain important elementsor dimensions may be determined in an expeditious manner, and at the machine by which the threads are being formed, so 6o that the machine operator may be guided as to proper adjustments of the machine to be made from time to time tending to correct the departures in either direction of such elements, or dimensions, from such mid-tolerance positions so that such departures may be maintained at all times within the tolerance limits. More specifically gauges by which departures from pitch diameters and lead of standard threads may be indicated will be hereinafter disclosed and claimed.

Snap and ring gauges for outside Work and plug gauges for inside, work, as heretofore constructed, have been subject to abrasion and wear which makes it necessary to establish tolerance boundaries for such gauges. The gauges of the present invention are opening and closing gauges 'designed to compare taps, screws and other threaded parts directlyavith a standard plug` gauge.l eliminating the need of the usual intermediate gauges and loss of size of gauges having more or less fixed adjustments due to wear of use. The fact that Ythese gauges are open and closing gauges prevents Wear thereon when the work yis inserted or removed and they may be compared frequently with an inspectors gauge or even the standard gauge, if desired, without appreciable Wear on those gauges. The plug gauge is the only member of the 9 screw familyY which can be made with great accuracy and it alone is thus suitable for use as the foundation of all thread measurements includingr both external and internal threads. The gauges of the *presentl invention, also, close with stress on the threads to be tested thus tending to even out surface inequalities throughout practicallyy the entire thread cirsubstantially the same manner as when the thread is in service.

In general, each of these gauges compr1ses a plurality of threaded members engageable with standard threads with a relatively loose fit, and so carried or mounted that their threads are capable of measured relative motions into pressing engagement with the threads of the standard threaded member and of those members to 'be tested, variations in the extent of such motions, when applied to 'standardthreads to those to be tested, indicating in amount and direction variations of the threads to be tested from the standard threads.

' Relative movement'pf the threaded members in opposite directions axially to bring the side faces oftheir threads into contact vwith opposite side faces of the standard thread gives, by the extent of such relative movement, an indication of the flank thickness of the standard thread, and variations iny the extent of such movement ,required to bring the side faces of the threads of these members into contact with the opposite side faces of the threads to be tested indicate variations in flank thickness of the threads to be tested from those ofthe standard thread'.= Flank thickness (i. e. the thickness of a thread from flank to flank measured at the pitch line) is a true measure of the strength of the thread and heretofore has been arrived at indirectly by measurement of pitch dialneter which is a definite function only of flankv thickness, depending on the angle of the thread faces. lVith the usual angle of 60 variations of pitch diameter cause .577 of those amounts in corresponding variations of flank thickness at the pitch line.

As measurement of pitch diameter as heretofore practiced is made at single points only it may give a local measurement only which may not truly indicate the vstrength of the thread in service Where the bearing of the mating thread thereon is over an extended area. Such measurements are reliable onl when made on especially prepared smooth threadsand are not suitable for testing the relatively rough surfaced threads produced by the usual thread forming machines.' The contact between the threads of the gauge members of the present invention and the threads to be tested is similar to that which the threadsl to be tested have with their mating threads in service, except that it does no extend so far toward the `thread roots due to the slight difference in size of the threads of the gauge members from that of the work with which the threads to be tested are 'intended to engage.

Differences in permissible axial movement between the two gauge members when applied to standard threads and threads to' be tested represent dill'eren'ces in relative position of the corresponding faces ofthe.

in one or the opposite direction relative to each other. If there is a lead error these permissible movements will be unequal for these opposite movements of the gauge menibers, the extent of this inequality indicating the extent of lead error. These gauges thus may indicate lead error as well as flank thickness or pitch diameter error.

The threadedmembers of my gauge may, if desired, be permitted a relative movement transverse to thethread axis, the extent of such movement permitted by the specimen tested giving a direct indication of the pitch diameter. Where the pitch diameters of the threaded gauge elements do not differ too widely from that of, the specimen so that the helix angles are not greatly different, a

.more extensive area of engagement is produced on those portions of the thread surface most effective in taking stress, than in\ the case ofmeasuring devices forl the same purpose heretofore used in so far as am aware. As will more fully appear also, the same members may be mounted to permit relative movements both axially and transversely.y

For a more complete understanding of-this invention, reference may be had to the accomv'panying drawings illustrating various embodimentsof my invention and in which Figure 1 is a section through a gauge for measuring flank thickness of external threads, this section being taken on the line 1 1 of Figure 2. L

Figure 2 is an elevation of the gauge shown in Figure 1.-

Figures 3 and 1 are perspectives showing' the internally threaded portions detached.

Figure 5 is an elevation showing a modified construction using a differential thread. -Figure 6 is a section on line 6 6 of Figure 5.-

Figure 7 is a section on line 7 7 of Figure 8, showing a somewhat modified construction also using a differential thread.

Figure 8 is an elevation showing a somewhat modified construction.

Figures 9 and 10 are sectional views of certain parts of the same construction.

Figure llis a 'section on the line 11 11 of Figure 12. c

f Figure 12 is `an elevation of a further modification.

Figure 13 is a det-ail section on line 13 13 of Figure 12. l

Figures 14 and 15 are plan views, illustrating/scale plates for indicating tolerances for different classes of fit.

Figure 16 illustrates a scale plate in which the variations from standard are indicated by percentages.

Figures 17 and 18 areV opposite face views of a still different construction.

Figure 19 is a section on line 19-19 of Figures 17 and 18.

Figure 20 is an elevation illustrating a `further modification.

Figure 21 is a. section on line 21-21 of Figure 20. Figure 22 is an end View of a gauge for testing internal threads.V

Figure 23 is asection on line 23-'23 of Figure 22.

Figures 24 and 25 are detalls, Figure 25l being in section, of parts of the construction illustrated in Figures 22 and 23. y

Figure 26 is a. section on line 26-26 of Fig-l ure 23. I

Figure 27 is an elevation' of a gauge for testing pitch diameters.'

Figure 28 is a lsect-ion on. line 28-28 of Figure 27. v'

Figure 29 is a detail of one of the parts shown in Figures 27 and 28. t

Figure 30 is an elevation showing a modified construction.

Figure 31 is a section on line 31-31 of Figure 30.

Figure 32 is an elevation showing a. further modiication. n

Figure 33 is a. section on line 33-33 of Figure 32.

Figures 34vand 35 are views similar to Figures 32 and 33, but showing further modifications.

Figure 36 is an edge View of the construction shown in Figures 34 and 35.

Figure 37 is a section on line 37-37 ot Figure Figures 38 and 39 are elevations showing a different construction.

yFigure 40 is a section` on line 40-40 of Figures 38 and 39.V Figures 41 and 42 are detail elevations of a part shown in Figures 38 to 40.

Figures 43 and 44 are elevations showing a different construction,L using a differential thread.

Figure 45 is a section on line 45-45`of Figure 43.-

Figure, 46 is a detail elevation.

Figure 47 is a diagrammatic section illustrating the .etfect of lead error in 'connection' with the construction of Figures 27 to 46.

Figure 48 is an end elevation of a. gauge for testing pitch diameters ot internal threads.

Figure 49 is a sect-ion on line L19--49 of Figure 48.

Figures 50 and 51 are sections on lines 1.50-50 and 51-.51, respectively, ot Figp ure 49.

Figures 52 and 53'are elevations showing parts in different positlons ot agauge. construction to test both Hank thickness and pitch diameter. f

Figure 54 is a section on line 54-54 of Figure 52.

Figure 55 is an end elevation of a gauge for internal threads having combined action.

Figure 56 is a section on line 56-56 of Figure 55. l

Figure 56 is a sectional view similar to Figure 56 but showing a slightly diierent structure.

Figures 57 and 58 are sections on lines 437- 57 and 58--58, respectively, of Figures 56 and 57.

Figure 59 is a central cross section through a gauge somewhat similar to the gauge shown in Figures 5 and 6, the gauge members in this figure being in open position and showing a screw of a size within the tolerance limits and of proper lead positioned therein.

Figures 60 and 61 are end elevations showing corresponding positions of the indicator elements, Figure 60 showing tolerance limit markings, while Figure 61 shows graduations in pitch diameter difference. x

Figures 62 and 65 are each similar to Figure 59 but showing the gauge members relatively adjusted to opposite closing limits, respectively.

Figures 63 and 64 are similar to Figures 60 and 61, respectively, but showing the parts in similar position to` Figure 62. l

Figures 66 and 67 are views similar to Figures 60 and 61, respectively, but with the parts in the adjusted position of Figure 65.

Figures 68 to 73, inclusive, are views similar to Figures 62` to 67, respectively, but show the\ga`uge members applied to a screw of short lead.

' Figures 74 to 79 inclusive are views similar to Figures 62 to 67, respectively, vbut showing the gauge membersas applied to a screw of long lead.4 l

Referring first to the construction shown in Figures 1 to 4, which illustrate a gauge for testing external threads, 1 and 2 indicate `eooperating internallythreaded members, each of these members being provided with internal gauging threads of the same lead as the standard external threads of the size to be tested and of a pitch diameter at least as great as the maximum tolerance limit for the class of tit desired.' The member 1 is shown as provided for slightly more than half its circumference with a marginal flange 3 provided with an overhanging lip 4, lthis lip formingwith the inner faceof the member l a socket to receive the inen'iber 2. permitt ing the member 2 to be rotated relative to thc member 1, buty preventingit from axial movement relative thereto. In order that the. ineinber` 2 may be inserted in and removed from this socket, opposite diametrical portions may be flattened off as shown at 5 and 6 sutticiently to decrease the over-all dimensions of the member 2 at this diameter so as to pass between the nearest marginal edges 7 and 8 of the flange portion 3. These flattened of portions are arranged at such an angular relation to the internal threads of the member 2 that when oneof these, such as the portion 5, is positioned half way between the edges 7 and 8, the internal or gaging threads of the members 2 and 1 lie in a common helix. When the members 1 and 2 are in this angular relation the gauge is in its open condition and a threaded member, either standard or to be tested, may be screwed freely thereinto, thethreads in this condition making a sufficiently loose fit with the standard threads as to permitthrea'ds of "the maximum tolerance dimensions tobe inserted. The angular" position of the-.members l and 2 when in this open position may be indicated by a suitable mark on the exposed face of the member 2 registering with a mark on the adjacentsurface portion of thelip 4.

. 'Assume now that a standard threaded plug'of the proper size be screwed into the parts 1 and 2 of this gauge, these parts beingv in their open position. By relative rotation their internal threads may be moved out of a common helix until the threads of the two members bind against the threads of the standard plug. The', reason for this will be evident when it' is considered that with the plug held from rotation the member 2 Vacting as a nut thereon will tend to displace the plug axially in one or the other direction,v

depending on the direction of rotation of the member 2. Such axial displacement can be eifected only until -one'side or the other of the sides of the plug thread-which, depending on the direction of rotation of the member 2 and the consequent direction of motion ofthe plug,-in1pinges on the'corresponding side of the threads in the member 1. In other words, relative rotation between the members 1 and 2 causes an apparent travel of their threads toward or from each other even though there is no relative bodily axialmovement of the members themselves. When the members are in threaded'engagement with a screw, such apparent relative movement' of the threads of the two members necessarily results in an eventual binding of these threads on opposite flanks of the screw thread with which the members are engaged. The extent of turning in either direction, therefore, represents "the position of the side faces of the threads yin the plug,

the limit of rotation of the member 2 in onef tested is substituted for the standard plug and the member 2 is rotated lin opposite directions as far as is permitted, the extent of such rotation furnishes an indication of the position of the corresponding side faces of the lthreads to be tested. If the'extent of turning is more than that permitted when the standard plug is in position, it will indicate that the flanks of the threads tested are thinner at the standard pitch line than those of the standard, 'while if the extent of motion permitted is less than vin the case of the standard thread Hanks, indication that the threads are thicken than; standard is given. If the 'difference in the extent of turning permitted for the threads to be tested and the standard threads is unequal in opposite directions, it means that the threads being'tested are positioned dii'erently from those of the standard, this indicating a lead error in the threads being tested.

As workmen are atv present accustomed to use variations in pitch diameter as anindication of thread diiferences, the scale on the member 2 may be correspondingly -graduated in pitch diameter differencesl The measuring of flank thickness directly, howeveris more liable to be accurate than-the measuring of pitch diameter for the reason that the thread faces may be quite inaccurate `so that pitch diameter may n ot give an accurate indication of. thread strength.

As shown in Figure 2, a pin 9 may be fixed in 'a radial perforation 9a in the member 2, this -pin serving as a handle by which :the member 2 may be turned and likewise preventing the member from being turned to an extent sufficient,` to permit it being `re moved from its Socket in the member 1. AS shown also in Figures' 2 and 3 the outer edge 'of the member 1 may be grooved,

roughened, or otherwise formed so that it may be securely grasped. n Dueto the binding action of the threads of the members 1 and 2 on the specimen being tested, the surface inequalities of the threads of this member are pressed down, thus giving a thread measurement of threads 'in a conditionsomewhat comparable to that when in service. The engagement of the" gauge members on the threads is over an extended area and over 'those portions of the thread which take the major portion of the stresses in service, the greatest dii'erence being that due to the yfact that as the threads of the gauge element are oversize and loosely fit the threads of the specimen they do not reach so far towardthe roots of thethreads tested as would the threads in a hole of the best size to receive these threads.

.I do not herein claim specifically the structure shown in Figures 1 4: -of the draw# ings, nor the specific method Aof gauging in? herent in the use of this particular form ot gauge as described, such subject matter being set forth and claimed in my copending application Serial No. 234,116` filed November 18, 1927. Y

It will be'noted in the construction just described that no relative axial motion bodily is permitted between the members 1 and 2, although the rotation of one of the gauge elements first in one direction and then in the other has the effect of causing the threads thereon to advance or push axially first against the flanks on one side of the thread beingtested and then against the flanks on the other side thereof. If nowksuch bodily axial motion be permitted but so controlled that the threads may lie in a common helix at one angular position only, a proportional increase of the angular motion with a consequent magnificationin indication over that of the construction just described may be effected. A gauge in which use is made of this action is illustrated in Figures 5 and 6/ and somewhat diagrammatically in Figures 59 to 79. Referring to Figures 5 and 6, 10 indicates one of the threaded members internally threaded at 11 to form gauging is externally threaded to mate the internal threads of the socket 12. This member 14 is shown as provided with a pair of outwardly extending pins 16 by which it may be rotated relative to the member 10.

By rotation of the member 14 relative to the member an axial motion between these members is produced, but as the lead of the mating threads between these members is 4different from that of their internal gauging threads,these threads are differential and Vthere is'one relative angular position only within the limits of gauging motion where t-he internal threads of the two members lie in a common helix. -As a matter of convenience the threaded engagement between the membersl() and 14 is made with a lead somewhat smaller than that of the internal gauging threads, and the confronting faces of the members 10 and 14 are somewhat spaced apart, as shown in Figure 6, when in that angular relation wherein the internal gauging threads lie in a common helix. If the memto be tested, the confronting end faces of thev two members approaching or receding from each other depending on the relative direction of rotation. As shown in Figure 5, the member 14 has an index indicated thereon which 'comes opposite to a zero indication on a scale 17 on the adjacent face of the member 10 when the gage is set to basic size of the plug, there being one such position when the gauge members are turned in either direction away from open position where the gauging threads lie in a common helix. At either side of these zero point-s on the scale 17 are indications to which the zero mark on the member 14 may be broughtas the member 14 is rotated in opposite directionsas far as is permitted by the work in the gauge, and as the member 14 moves axially during its rotation but at a less rate than the pitch of the gauging threads it may be given a more extensive angular movement for the same piece of work than can be given the member 2 of the form firstdescribed which is not permitted any bodily axial movement. Provision of the socket 12 permits the gauging threads of the two portions to be positioned closely together' while permitting a desirable length of'thread engagement betweenthe parts 10 and 14, even when the member 14 is screwed outwardly from the member 10 to a considerable extent.

In order that the action of the gauge members when a. differential thread is employed may be more fully appreciated, certain more or less diagrammatic showings of a gauge construct-ed somewhat similar to that shown in Figures 5 and 6 have been shown in Figures 59 to 79. Referring to these figures, it will be seen that the gauge comprises a pair of ring gauge members 300 and 301, one of these members, as 301, being fixed to a ring 30.2 which has an internally threaded'portion 303 with ,which external threads on the member 300 engage. f As shown, the fixing of the member 301 is accomplished by the use of a ring 310 pinned thereto by pins 311, the ring 310 being fixed as by screws 312 to the ring 302.v Pins 314 projecting beyond the outer face of the ring 300 may be engaged by the fingers to facilitate turning of the member 300. The threads at 303 are shown asof less pitch than the gauging threads of the members 300 and 301. When the member, 300 is` in such angular' positionlthat its outer face is flush with the corresponding face of the ring 302, its gaging threads lie in the same helix with the gauging threads of the member 301 and a mark or arrow 304 on the member 300 points to the open position marking on the ring 302, as shown in Figures 60 and 61. In Figure 60 the ring 302 carries tolerance limit indications on either side of the open position, while in Figure 61 the end face of the ring 302 is provided with graduations showing pitch diameter differences in thousandths of an inch. Ordinarily for common shop use the gauge is provided with indications to show the tolerance limits or bounds of tolerance, since the specimen being testedl is accepted when, on being subjected to the gauging operation, the indicator or mark 304 stops oneach rotative movement of the element 301 between the marks indicating the bounds of tolerance.

When the arrow 304 is brought opposite to the open position indication on the ring 302 so that the gauging threads of both gauging lmembers lie in a common helix, the gauge is inits open position so that it will admit the screw 305 with a loose lit, as shown in Figure 59. If now the member 300 be rotated clockwise when viewing the gauge from the` end face bearing the indications, the arrow 304 may be brought within the tolerance limits into the position shown in Figure 63. When in this position the member 300 has been screwed inwardly so vthat it takes the position shownin Figure 62, its end face being somewhat to the left `of the end face of the member 302. In this figure it will be noted that the right hand faces of the gauging threads of the member 300 as at a are brought uph snugly against the left hand faces b of the threads being gauged, while the left hand faces 0 of the gauging threads'of the' member 301 engage snugly against the right hand faces d of the corresponding threads of the screw 305. If now the member 300 is rotated counter-clockwise as far as it is permitted with the screwv 305 in position, the .are row 304 may be moved past the open position to the position shown in F Fgures 66 and 67.

Here also the arrows liewithm the tolerance limitstheirlimit of motion beingthe same distance to the lefthand side of the open position as their opposite limits of motion were to the right of thisopen position. This indicates a correct lead forthis screw. When in this position theend face of the member 300 is somewhat to the right of the end face of they member is in contact with the mating thread face of the screw305 at any time.

Assume now that instead of the screw. of `the correct lead, a screw of short lead` be Only onev face of the gaugingthreads of each gauging.

placed in the gauge members when they have been turned to suiiiciently near open position to receive the screw readily. The member 300 is now turned clockwise until the right hand face a of the gauging threads Jof themember 300 engages the left hand face o of the thread being tested and the left hand facel c of the member 301 is brought against the right hand face al of the thread'being gauged, the arrow 304 taking the position shown in Figures 69 and 70. As shown, this is between the tolerance limit space and the open position, and indicates either an oversize pitch diameter, or the presence of lead error, or both. i

If now the member300 be tui-ned in the` opposite direction as far as possible until its left hand face c engagesthe right hand'faces f of the screw and the right hand face g of the member 301 is brought against the left handface h of the screw, the arrow 304 is4 brought a considerable distance further from the'open position in counter-clockwise direction than it was in a clockwise ldirection when the gauge member 300 was turned in that direction. This means that the gauge member 300 can move further inwardly than can move outwardly until it is stopped by the threads being gauged, and that consequently these threads are closer together than the pitch of the gauging members, or in other words, that the lead is in error, being too short. If the arrow 304 moves to the left beyond `the basis mark, as in F igure-72, or beyond the zero mark, as in Figure 73, this shows that the pitch diameter is actually undersize.

It is obvious that when there is nolead error present in the thread of the screw 305, the threads of the gauge members 300 and 301 when set up on the screw will yengage the screw along their entire length. That is, every convolution of the threads of these members will engage the thread of the screw 305 as shownV in Figure 62. VVthen however the screw 305 has a lead error, then the threads of the members 300 atnd 301, hauing correct lead, can each engage the .threadfof the screw over a small portion offene convolution only (provided the lead error is fnot so excessive as to cause the` screw toengage each' member 300, 301 at two points); As shown in .Figures 68 and 71, these single points of contact of each member 300, 301 with the thread of the screw305 will be at4 their outermost convolutions when the members are set np in one direction (Fig. 68), and at their innermost convolutions when the members are set up in the other direction Fig.

71). Assuming thatthe thread of the screw is of reasonably regular and symmetrical profile. the flank thickness of a screw with a short lead may be obtained byfturning the member 300 to the left as in Figures 72 and 7 3 since this results in engagement of two successive turns of the thread of the screw 305,

the other turns not being touched by the mem-v bers 300, 301. As the lead error between two successive turns of a threwl is negligible, a fairly accurate indication of flank thickness of the thread is thus'obtainable by rotation of the member 300 to the left. On the other hand, where the sca ew thread lead is short, rotation of the member 300 to the right (as in Figs. 68, 69 and 7 0) will cause engagement of the screw by the members 300, 301 at the outermost or mest. widely separated turns of the latter (Fig. (38). Thus the effect of the lead error over a distance of several turns of thread will appear when the member is turned to the right (Figs. 69, 70)-, this offset being modified to some extent by any error oft' flank thickness which may be present in thescrew 305.

Assume now that a screw having too long aflead is inserted in` the'gauge, the gauge being brought'sufliciently near its open position for thisA to be inserted and the gauge member 300 is turned first in clockwise direction and then in counter-clockwise direction as Lfar as is'permittedby the screw in l the gauge, the condition illustrated in Figures 7 4 to 79 will occur. When the member 300 is turned clockwise so that the right hand gauging thread face a engages the left hand thread face b of the screw being tested and the left hand face c of the member 301 engages the righty hand face (Z of the screw, the arrow 304l is brought to the positions shown in Figures and 76, while when the 4member 300 isv turned counter-clockwise so that its end face projected beyond the end face of the member 302, as shown in Figure 77, until its left hand thread face e engages the right hand thread face f of the screw and the right hand face g of the member 301 engages the left hand face L of the screw, the arrow 304 is brought to the position shown in Figures 78 and 79. As the lead here is long, the member 300 may be screwed in or clockwise from the gauge -open position further than it can be screwed out, this being shown by differences in the angular position of' the arrow 304 from the open position when turned in these directions. As shown'the arrow 304 when turned clockwise goes beyond the range of tolerance limits as shown in Figure 75, or to between 5/1000 and 0,/1000 of an inch small pitch diameter as shown vin Figure 76, while when turned in the counter-clockwise direction it does not reach the tolerance limit range, showing be-V tween 4,/ 1000 and 5/1000 of an inch oversize in pitch diameter. This inequality of permissible. movement of the gauge member 300 in opposite directions indicates a lead error and that the lead is long. As hereinbefore stated, the presence of lead error in the thread of the screw 305 results in contact of the screw 305 at one point only with each of the members 300. 301, these two points being on either the twoinnermost or the two outermost turns of thethreads ofthe members 300, 301 according to the direction in which the member 300 is rotated when the gauge is set up on the screw 305. If the lead error of the screw is long, rotation of the member 300 to the right or clockwise as in Fig. 75 results in engagement of the members 300, 301 with the screw 305 at points Z) and (l (Fig. 74) which lare close together. Thus the effeet of the lead error in this instance is practically eliminated and the flank thickness is indicated by the angle of rotation of the member` 300. On the other hand, turning the member 300 to the left (Figs. 7 8, 7 9) results in engagement at the outermost of most widely separated turns e, g of the members 300, 301 (Fig. 77) so that the effect of the lead error over several turns of thread is indicated by the angle of rotation of the member 300 to the left, this indication being modified by any error of flank thickness which the screw 305 may have. In using a gauge of this type, the presence of lead error may be observed by the lack of equality between the angles of rotation of the member 300 in opposite directions from the open position. In'such case, the position of greater angular displacement indicates the flank thickness of the thread being tested -while the opposite position of the member 300`indi- Cates the lead error over several turns of thread modified by the flank thickness error, if any, of one thread. As shown both in connection with theshort lead of Figures 69 and 73, and in the case of the long lead -in Figures 74 to 79, the screw does not come within the tolerance limits and hence must be rejected. lf it does not fall within the tolerance limits when turned in either direction, it is so far from thefstandard size. as

to vbe rejected.' Vhen there is a lead error, it will be noted that the gauge indications do not represent true indications of pitch diameter.

It will be seen that in the use of this gauge,

when the gauge members are turned relative to each other in either direction, the threads of one gauge member engage the fiankson one side only7 of the threads of the member being tested, while the threads of the other gauge member engage only the flanks on the other side of the. threads being tested, and that-by turning the gauge members relative to each other first in one direction and then in the other, the gauging threads of each member are caused to engage first on one flank and then on the opposite flank on the threads ofthe member being tested. I

In Figures 7 to 10 a slightly modified construction is shown, in which the similar inthe ring 22 as by means of a set screw 23, while the other may be permitted a rotary movement with relation to the ring 22 and may be held normally in its gauge-open position relative to the member 21 by means ofa spring pressed pin 24 carried by the ring 22 and engaging in a depression 25 in a member,26' made fast to the outer face of the member 2O as by means of the screws 27. This member 26 may have a handle portion 28 and an indicator pointer 29 movable over a scale on the adjacent face of the ring 22,'as shown best in Figure 8. The member 21 may also have fixed lthereto a similar handle member 29a.

to facilitate holding this member against rotation when it is desired to rotate the gauge member 20. 4' l In Figures 11 to 13 a further modification is shown. In this" construction the gauge members 30 and 31 have threaded engagement .with the ring 32 by a thread having a lead different from that of the gauging threads, and these gauging-members 30 and 31 are shown as of greater axial length'than the gauge members 20 and 21 heretofore described andare provided with gauging threads for substantially one half the lengths of ltheir internal bores.` These members 30 and 31 may be assembled either end out, as shown f their internally threaded portions being placed adjacent to each other. Each is provided with a disk face or plate portion 'as 33 and 34 fixed thereto as by screws 37 and provided with a handle extension 35 and 3G, re-

` spectively. The plates 33 and 34 may be fixed to either face of the corresponding gauge member, being fixed to that which 1s ositioned outwardly. On the ring 32 may lie secured a two pieced ring member 40, U shaped in cross section which-extends over` the outer faces of the member 32 and partially masks the scale 41 which may be marked thereon. This masking portion 42 covers 1ndications except those within the tolerance A limits for any particulan class of fit desired whichv are alone exposed. F or example aS shown in Figure 12, a class 1 fit is designated,

all the graduations below 3 and above 9 being masked. Either of the ring members '30 or 31 may be fixed to the ring 40 at' will. For this purpose the ring has diametrically opposite openings within which extend inturned ends 45 of a stirrup member 46 which` may be swung-so that its central part 47 engages either one ofthe lugs 48 on the handle portions 35 and 36 to hold the corresponding gauge member against rotationrelative to the ring. The gauge members 3Q and 31 may be held in their open condition with theirggauging threads Ilying in a common helix, and for this purpose the construction.

shown in Figure 13 may be employed. Re-

ferring to this yfigure it will be seen that the members 30 and l'31 ihave pe'rforations` 4:9` which are vin'axial alinement when thegaugemembers are in open position. When in this position a spring 50 in onel of these perforations holds a pin 52 extending across from one of these perforations to the other. This pin may be retracted into one of these perforations by pressure exerted on a pin 53 slidable in the other perforation and having a reduced portion 54 projecting through one face of the gauge. The mating ends of the pins 52,a1id 53 are preferably rounded so that when the pin 52 is retracted to approximately the face of the corresponding gauge member these gauge members may be turned relative to each other.

Figures 14 and 15 illustrate different forms of scale plates, Figure 14 being somewhat similar to Figure 12 except that the masking member 4() is arranged to show the range of tolerance for class 3 fit which is smaller than for class 1 fit. In Figure 15 no masking plate is employed, but the range of tolerances for' the desired class of fit is shown on a ci-rcumferential zonel different fromA those indications without the desired range'. j

Figure 16 illustrates a scale calibrated to show the percentage of normal Hank thickness rather than in 'pitch diameter variations. The-calibration of the scale to read in terms of percentages lof the normal flank thicknessof the screw to be tested has certain advantages over a scale calibrated in terms of fractions of an inch or other definite unit of length. The holding strength f a screw (or. the shearing strengthof'its thread) depends to a large extent on the flank thickness of its threadV so that deviations from normal Hank thickness result in approximately proportional reductions in holding strength. Aneerror of7 one thousandth of an inch may be negligible in the fiank thickness of a relatively large screw but may be prohibitive in the? caseof a smaller screw,'hence the significance. of an error expressed in frac-V tions of -an'inch depends on the size of the screw tested. But an error of flank thickness 'expressec asa percentage of normal flank thickness gives at once an approximate indication offthe holding strength of the screw, regardless of'its size, compared to what it should Jbe ifthe screw had a perfect thread.

fFigvfures 17, 18 and 19 illustrates a gauge intended to be operated by one hand but which will not indicate lead error and which is ytherefore only accurate to indicate flank thickness or pitch diameter error where there is no lead error'. In this construction the gauge members having the internal gauging threads are shown at 6() and 61, being engaged with a differential thread,-that is, a thread with a uifi'erent lead than the gauging threads-#with the marginal holding ringr are normally and resiliently held in their open position with the gauging threads lying in a common helix by means of a coil spring 61 seated in mating sockets 65 in the two gauging members and having one of its ends fixed to each of these members. The ring member 62 which carries the scale on its end face may have a masking member 66 showing the required tolerance boundaries detachably fixed thereto, and each of the members 60 and 61 may have handle extensions 'as at 67 and 68, as shown in Figures 17 and 18. These extensions 67 and 68 may have knobs 69`at their outer ends to facilitate'their engagement bythe operators fingers. In normally open position ofthe parts the finger portions 67 and 68 are spaced apart as shown in Figures 17 and 18. When the screw to be tested has been inserted, these finger portions may be brought together, thus turning the members 60 and 6,1 relatively until their gauging threads bind upon the work, thus indicating by comparison with the extent of motion permitted when a standard plug is in the gauge, variations from this standard of the threads of thepiece being tested. g

In Figures 2O an'd 21 a further modification is shown in which one of the gauging members as 70 may have a tubular handle portion 71 fixed thereto in which the threaded member to be gauged may extend. As shown the other gauge member 72 having the mating gauging threads is provided with the handle plate 73 which may be fixed to the retaining ring 74 as by means of the stirrup 75. In this construction the outwardly directed lfiange 76 of the tubular handle 71 is shown as formed at one point with an indicator pointer 77 which cooperates with a scale on the adjacent face of the ring member 74, which may, if desired, be partially masked by the tolerance boundary member 78.

The same principle of gauging may be applied to the measurement of internal threads and with'the same degree of accuracy, a result whichheretofore, so far as I am aware, has not been possible. A construction for 'this urpose is illustrated in Figures 22 to 26. `or internal thread gauging the gauging members are provided with external threads, each of the standard lead and each ot' as'ize less than basic to the maximum tolerance, both of which may be inserted in the work and turned relatively in opposite directions to bring their thread faces into en l gagemeut with'the corresponding thread faces of the internal threads.

In order to procure a magnification oil motion so that variations may be more Ireadily detected, use may be made, if desired, of differential thread connection between the gauging members as shown in certain of the constructions hereinbefore described for gauging external threads. All of these constructional features i are embodied in the gauge shown in Figures 22 to 26 for the gauging of internal threads.

lmating the threads 82. The other end of the sleeve 83 is rovided with external gauging threads 85 w ich cooperate with the external gauging threads 81 of the member 80 in testing the work.v Adjacent to the threaded portion 84 the sleeve 83 is provided with -a anged extension 86 on the outer face of which are graduations as at 87 with which cooperates a pointer 88 carried by a head 89 fixed to the threaded end portion 82 of the member 80 as by means of a set screw 90. At one angular relation of the gauging threads 85 and 81 in which they are somewhat separated axially their threads lie in a common helix. This is the open position of the gauge at which it may be screwed into the internally threaded member to be tested or into the internally threaded member with standard threads. The parts may be normally held in this gauge-open osition .by means of the removable pin 91. fter the gauging threads 81 and 85 are within the work the pin 91 .is withdrawn and the head 89 is rotated relaamount of difference when engaged in the work to be tested and in the, standard threads when rotation is effected in' opposite directions indicates the presence of a' lead error in the internal threads which are to be tested.

Not `only may itch diameters or flank thickness be teste by relative axial move ment of a pair of'threaded gauge members as has been described, but it may also be measured ,-by a relative transverse motion between two such threaded members, and where threaded members are used for this purpose greater accuracy is ordinarily obtained than by the use of the usual snap gauges 4for the reason that the engagement of the'gauge members with the work to be tested is over a more extended/length of thread, provided however that the diameterdifferences oi the gauge and the work to be tested are not so great as .to introduce error construction isshown in which the member 120 has acam face 121 which 1n use,

due to the diiference in lead angle for the two different diameters.

Constructions wherein such relative lateral motion of the threaded' members is utilized are Ashown in Figures 27 to 46 inclusive. In Figures 27 to 37 this transverse motion 'of one of the threaded members relative to the other may be accompanied by a rotating motion about the axis of either threaded member. In the construction shown in Figures 38 to 46 no such rotary motion of the threaded member moved is permitted.

In the construction shown in Figures 27 and 28, 100 indicates the laterally movable gauge member, whichas shown, is positioned between spaced internally threaded portions 101 of a block 102. The member 100 may be held in its-operrposition relative to the member 102 with its internal threads in axial alinementwith the threads of the portions 101 and in such angular relation thereto as to lie in a common helix therewith, by any suitable means. such as the spring pin 103 seated in a socket therein, the end of which may be depressed to substantially coincide with an end face of the member 100 by means of the pin 104 having a reduced extremity 105 projecting through one face of the member 102. The periphery of the member 100 is not concentric with the gauging threads, but is arranged as a cam surface at 106 (Figure 29) riding against the reduced extremity 107 of a plug 108 threaded through Athe member 102. The plug may be fixed in position relative to the member 102 as by means of a. set screw 109. On rotation of the member 100 relative to the member 102, therefore, the bearing of the cam face 106 on the end of the plug 108 acts to force the member 100 so that its gauging threads are moved out of axial alinement with the gauging threads of the portions 1,01 thus to give a shearing action to the member 100 as-far as is permitted b v its engagement of.the threads on the member to be tested. The extent of such motion permitted may be indicated by the angular position f the member 10Q, a scale along its edge with which a fixed line on the member 101 may cooperate showing such angular position'. A shearing motion without the. rotary motion may be imparted by rotation of the plug 108 and for the purpose of measuring the extent ot such motion an indicator point 110 may cooperate with graduations 111 marked on the periphery of a head 112 on the outer L1end of the threaded plug 108. l

In Figures 30 and 31 a somewhat dill'erent auge bears against the end of a plug 122 extending through a marginal Wall member 123 of the other threaded p gauge member 124. This vmarginal wall member 123, as shown in Figure 30, extendsl somewhat more than one Vhalt` the circumference about the member 120 which may be cut oil at one or more points sutliciently to permit it to be placed in posi. tion within the marginal flange 123. This flange is lprovided with a lip portion 125 extending over the outer face of the gauge member 120 and normally retains the mem` ber V120 in position. At the flat face portion of the member 120 may be fixed the pointer 126 which acts to prevent the member 120 b6- ing turned to such an angular position that it may be removed from the member 124 and which also acts in cooperation with graduations on a flange portion 128 of the member 124 to indicate the extent of motion permitted -the gauge member 120 when a standard screw or a screw to be tested is engaged by the .gauging threads of the' members 120 and 124.

If it isdesired to eliminate any wedging action caused by the rotation of the threaded member in either of the constructions shown in Figures 30 and 31 or 27 and 28 so that the only eH'ective gauging motion is that transversely of the axis of the threaded. member, this may be done by permitting tree axial motion of the movable gauge member so that it may seat itseli:l on the threads of the threaded member engaged thereby without reference to the changing angular relation between the gauge member and the member tested as the gauge member is given its transverse motween the stationary gauge members 131 and 132, the member 131 being provided with a peripheral flange 133 within which the member 132 is engaged and there fixed by means such as the set screw 134. The movable `a5 tion. This is shown in Figures 28 and 31 in member 130 is provided with an edge cam p -portion as 135 which engages an abutment 137 in which rides a pin 138, the linner end of which engages in an opening inthe member 130. This pin 138 serves as a handle by which the member 130 may be rotated, its enp gagement with -the screw 136 causing it to be given a motion transverse to the axis of the gauge thread openings of the members 131 and 132.. This pin 138 may be provided with an index pointer 139 cooperating with a scale marked on the outer face of the flange mem ber 133 adjacent thereto. The space within whichthe member rotates may be made somewhat wider than the thickness of the member 130 in order to permit a free axial play to follow the lead of the screw as the member 130 is rotated, thus to prevent any mot-ion except the transverse motion nom being cllcctive as a gauging motion. 

